[Profiler] Introduce error branch ProfileCounterRefs

These reference error branches for AST nodes that
can throw errors.

Author: hamishknight

include/swift/SIL/SILProfiler.h

@@ -36,9 +36,10 @@ class ProfileCounterRef final {
 public:
   enum class Kind : uint8_t {
     /// References an ASTNode.
-    // TODO: This is the currently the only kind, but it will be expanded in
-    // the future for e.g top-level entry and error branches.
-    Node
+    Node,
+
+    /// References the error branch for an apply or access.
+    ErrorBranch
   };
 
 private:
@@ -56,6 +57,12 @@ class ProfileCounterRef final {
     return ProfileCounterRef(node, Kind::Node);
   }
 
+  /// A profile counter that is associated with the error branch of a particular
+  /// error-throwing AST node.
+  static ProfileCounterRef errorBranchOf(ASTNode node) {
+    return ProfileCounterRef(node, Kind::ErrorBranch);
+  }
+
   /// Retrieve the corresponding location of the counter.
   SILLocation getLocation() const;
 

lib/SIL/IR/SILProfiler.cpp

@@ -173,7 +173,15 @@ SILLocation ProfileCounterRef::getLocation() const {
 
 void ProfileCounterRef::dumpSimple(raw_ostream &OS) const {
   switch (RefKind) {
-  case Kind::Node: {
+  case Kind::Node:
+    break;
+  case Kind::ErrorBranch:
+    OS << "error branch of: ";
+    break;
+  }
+  switch (RefKind) {
+  case Kind::Node:
+  case Kind::ErrorBranch: {
     OS << Node.getOpaqueValue() << " ";
     if (auto *D = Node.dyn_cast<Decl *>()) {
       OS << Decl::getKindName(D->getKind());
@@ -190,6 +198,11 @@ void ProfileCounterRef::dump(raw_ostream &OS) const {
   switch (RefKind) {
   case Kind::Node:
     Node.dump(OS);
+    break;
+  case Kind::ErrorBranch:
+    OS << "error branch of:\n";
+    Node.dump(OS.indent(2));
+    break;
   }
 }